Sensor module and measurement system

ABSTRACT

A sensor module includes: an inertial sensor; and a processing circuit processing an output signal from the inertial sensor. The processing circuit varies processing of the output signal according to a sampling period for acquiring the output signal. The processing circuit may change the sampling period for acquiring the output signal according to a content of processing of the output signal.

The present application is based on, and claims priority from JPApplication Serial Number 2021-054956, filed Mar. 29, 2021, thedisclosure of which is hereby incorporated by reference herein in itsentirety.

BACKGROUND 1. Technical Field

The present disclosure relates to a sensor module and a measurementsystem.

2. Related Art

For example, JP-A-2019-163955 describes an inertial sensor unit havingan angular velocity sensor device, an acceleration sensor device, and amicrocontroller that processes an output signal from the angularvelocity sensor device and the acceleration sensor device and outputsthe processed output signal to a host device. The inertial sensor unitis also referred to as IMU (inertial measurement unit).

However, JP-A-2019-163955 does not disclose or suggest a sampling periodof the output signal. As the sampling period becomes shorter, aquantization error in converting the output signal (analog signal) to adigital signal becomes smaller but signal processing that can beexecuted during the sampling may be limited. On the other hand, as thesampling period becomes longer, the quantization error in converting theoutput signal (analog signal) to a digital signal becomes greater butthe signal processing that can be executed during the sampling is lesslikely to be limited. In this way, the quantization error and thelimitation to the signal processing are in a tradeoff relationship.Therefore, how the sampling period is decided is important.

SUMMARY

A sensor module according to an aspect of the present disclosureincludes: an inertial sensor; and a processing circuit processing anoutput signal from the inertial sensor. The processing circuit variesprocessing of the output signal according to a sampling period foracquiring the output signal.

A sensor module according to another aspect of the present disclosureincludes: an inertial sensor; and a processing circuit processing anoutput signal from the inertial sensor. The processing circuit changes asampling period for acquiring the output signal according to a contentof processing of the output signal.

A sensor module according to still another aspect of the presentdisclosure includes: an inertial sensor; and a processing circuitprocessing an output signal from the inertial sensor. The processingcircuit sets a content of processing to be performed on the outputsignal from the inertial sensor and a sampling period for acquiring theoutput signal from the inertial sensor, according to data requested by ahost device.

A measurement system according to still another aspect of the presentdisclosure includes: the foregoing sensor module; and a host deviceelectrically coupled to the sensor module.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an overall configuration of ameasurement system according to a first embodiment of the presentdisclosure.

FIG. 2 is a block diagram showing a circuit configuration of a signalprocessing circuit.

FIG. 3 is a block diagram showing signal processing in a first signalprocessing mode.

FIG. 4 is a block diagram showing signal processing in a second signalprocessing mode.

FIG. 5 is a block diagram showing signal processing in an angularvelocity mode.

FIG. 6 is a block diagram showing signal processing in an accelerationmode.

FIG. 7 is a block diagram showing an overall configuration of ameasurement system according to a second embodiment.

FIG. 8 is a block diagram showing signal processing in a third signalprocessing mode.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

The sensor module and the measurement system according to the presentdisclosure will now be described in detail, based on embodimentsillustrated in the accompanying drawings.

First Embodiment

FIG. 1 is a block diagram showing an overall configuration of ameasurement system according to a first embodiment of the presentdisclosure. FIG. 2 is a block diagram showing a circuit configuration ofa signal processing circuit. FIG. 3 is a block diagram showing signalprocessing in a first signal processing mode. FIG. 4 is a block diagramshowing signal processing in a second signal processing mode. FIG. 5 isa block diagram showing signal processing in an angular velocity mode.FIG. 6 is a block diagram showing signal processing in an accelerationmode.

As shown in FIG. 1, a measurement system 10 has a sensor module 1 and ahost device 5 electrically coupled to the sensor module 1. The sensormodule 1 is an IMU (inertial measurement unit) and has a 3-axis angularvelocity sensor device 2 and a 3-axis acceleration sensor device 3,which are inertial sensors, and a signal processing circuit 4 processinga signal outputted from each of these devices 2, 3. These devices 2, 3and the signal processing circuit 4 are coupled together via an SPI(serial peripheral interface), for example. However, the method forcoupling these devices is not particularly limited.

3-Axis Angular Velocity Sensor Device 2

As shown in FIG. 1, the 3-axis angular velocity sensor device 2separately detects an angular velocity cox about an X-axis, an angularvelocity coy about a Y-axis, and an angular velocity ωz about a Z-axis,and outputs data Dωx of the X-axis angular velocity, data Dωy of theY-axis angular velocity, and data Dωz of the Z-axis angular velocity,which are digital data.

The 3-axis angular velocity sensor device 2 has an X-axis angularvelocity sensor 2 x detecting the angular velocity cox about the X-axis,a Y-axis angular velocity sensor 2 y detecting the angular velocity coyabout the Y-axis, a Z-axis angular velocity sensor 2 z detecting theangular velocity ωz about the Z-axis, and a processing circuit 20processing detection signals from these sensors 2 x, 2 y, 2 z andoutputting the data Dωx, Dωy, Dωz.

The processing circuit 20 includes, for example, an analog circuitincluding an amplification circuit amplifying the detection signals fromthe sensors 2 x, 2 y, 2 z and a synchronous detection circuit performingsynchronous detection with respect to the detection signals, or thelike, and an A/D conversion circuit converting an analog signal from theanalog circuit to a digital signal, or the like. The A/D conversioncircuit performs A/D conversion of, for example, an analog signal of theX-axis angular velocity, an analog signal of the Y-axis angularvelocity, and an analog signal of the Z-axis angular velocity to digitaldata in time division.

However, the configuration of the 3-axis angular velocity sensor device2 is not particularly limited. For example, an X-axis angular velocitysensor device detecting the angular velocity cox about the X-axis andoutputting the data Dωx of the X-axis angular velocity, a Y-axis angularvelocity sensor device detecting the angular velocity coy about theY-axis and outputting the data Dωy of the Y-axis angular velocity, and aZ-axis angular velocity sensor device detecting the angular velocity ωzabout the Z-axis and outputting the data Dωz of the Z-axis angularvelocity, may be integrated together. Also, one or two detection axes ofthe X-axis, the Y-axis, and the Z-axis may be omitted.

3-Axis Acceleration Sensor Device 3

As shown in FIG. 1, the 3-axis acceleration sensor device 3 separatelydetects an acceleration Ax in an X-axis direction, an acceleration Ay ina Y-axis direction, and an acceleration Az in a Z-axis direction, andoutputs data DAx of the X-axis acceleration, data DAy of the Y-axisacceleration, and data DAz of the Z-axis acceleration, which are digitaldata.

The 3-axis acceleration sensor device 3 has an X-axis accelerationsensor 3 x detecting the acceleration Ax in the X-axis direction, aY-axis acceleration sensor 3 y detecting the acceleration Ay in theY-axis direction, a Z-axis acceleration sensor 3 z detecting theacceleration Az in the Z-axis direction, and a processing circuit 30processing detection signals from these sensors 3 x, 3 y, 3 z andoutputting the data DAx, DAy, DAz.

The processing circuit 30 includes, for example, an analog circuitincluding an amplification circuit amplifying the detection signals fromthe sensors 3 x, 3 y, 3 z and a synchronous detection circuit performingsynchronous detection with respect to the detection signals, or thelike, and an A/D conversion circuit converting an analog signal from theanalog circuit to a digital signal, or the like. The A/D conversioncircuit performs A/D conversion of, for example, an analog signal of theX-axis acceleration, an analog signal of the Y-axis acceleration, and ananalog signal of the Z-axis acceleration to digital data in timedivision.

However, the configuration of the 3-axis acceleration sensor device 3 isnot particularly limited. For example, an X-axis acceleration sensordevice detecting the acceleration Ax in the X-axis direction andoutputting the data DAx of the X-axis acceleration, a Y-axisacceleration sensor device detecting the acceleration Ay in the Y-axisdirection and outputting the data DAy of the Y-axis acceleration, and aZ-axis acceleration sensor device detecting the acceleration Az in theZ-axis direction and outputting the data DAz of the Z-axis acceleration,may be integrated together. Also, one or two detection axes of theX-axis, the Y-axis, and the Z-axis may be omitted.

Signal Processing Circuit 4

The signal processing circuit 4 has, for example, a processor (CPU)formed by a computer and processing information, a memorycommunicatively coupled to the processor, and an external interface. Aprogram executable by the processor is saved in the memory. Theprocessor reads and executes the program stored in the memory.

As shown in FIG. 2, the signal processing circuit 4 has a signalprocessing unit 40 processing the data Dωx, Dωy, Dωz, DAx, DAy, DAzoutputted from the 3-axis angular velocity sensor device 2 and the3-axis acceleration sensor device 3, a host interface 44 transmittingthe data processed by the signal processing unit 40 to the external hostdevice 5, and a mode selection circuit 45 changing the content ofprocessing by the signal processing unit 40. The signal processing unit40 has a first signal processing unit processing the data Dωx, Dωy, Dωz,DAx, DAy, DAz, a second signal processing unit 42 further processingeach data processed by the first signal processing unit 41, and a thirdsignal processing unit 43 further processing each data processed by thesecond signal processing unit 42.

The contents of the processing executed by the first signal processingunit 41, the second signal processing unit 42, and the third signalprocessing unit 43 are not particularly limited. In this embodiment, thefirst signal processing unit 41 is a filtering circuit eliminating anoise from the data Dωx, Dωy, Dωz, DAx, DAy, DAz and outputting dataDωx1, Dωy1, Dωz1, DAx1, DAy1, DAz1. The second signal processing unit 42is a temperature compensation circuit performing temperaturecompensation of the data Dωx1, Dωy1, Dωz1, DAx1, DAy1, DAz1 andoutputting data Dωx2, Dωy2, Dωz2, DAx2, DAy2, DAz2. The third signalprocessing unit 43 is a matrix calculation circuit performing matrixcalculation for coordinate transformation of the data Dωx2, Dωy2, Dωz2,DAx2, DAy2, DAz2 and outputting data Dωx3, Dωy3, Dωz3, DAx3, DAy3, DAz3.

The data Dωx, Dωy, Dωz, DAx, DAy, DAz may correspond respectively to thesensors of the 3-axis angular velocity sensor device 2 and the 3-axisacceleration sensor device 3. The data Dωx1, Dωy1, Dωz1, DAx1, DAy1,DAz1 may correspond respectively to the sensors of the 3-axis angularvelocity sensor device 2 and the 3-axis acceleration sensor device 3.The data Dωx2, Dωy2, Dωz2, DAx2, DAy2, DAz2 may correspond respectivelyto the sensors of the 3-axis angular velocity sensor device 2 and the3-axis acceleration sensor device 3. The data Dωx3, Dωy3, Dωz3, DAx3,DAy3, DAz3 may correspond respectively to the sensors of the 3-axisangular velocity sensor device 2 and the 3-axis acceleration sensordevice 3 or may be attitude data, position data or the like acquired bycomputing, for example. That is, the data Dωx3, Dωy3, Dωz3, DAx3, DAy3,DAz3 may or may not correspond respectively to the data Dωx, Dωy, Dωz,DAx, DAy, DAz.

The host interface 44 transmits the data Dωx3, Dωy3, Dωz3, DAx3, DAy3,DAz3 outputted from the signal processing unit 40, to the host device 5.The host interface 44 and the host device 5 are coupled together via anSPI (serial peripheral interface), for example. However, the method forcoupling these components is not particularly limited.

The signal processing circuit 4 has a first signal processing mode M1, asecond signal processing mode M2, and a third signal processing mode M3differing from each other in the content of processing of the data Dωx,Dωy, Dωz, DAx, DAy, DAz. The mode selection circuit 45 is a circuitselecting one mode from among the first signal processing mode M1, thesecond signal processing mode M2, and the third signal processing modeM3 differing from each other in the content of signal processing,according to a sampling period T or a content of processing requested bythe host device 5.

As the sampling period T becomes longer, a longer processing time can betaken to output data to the host device 5 after acquiring the data Dωx,Dωy, Dωz, DAx, DAy, DAz. Therefore, a greater amount of signalprocessing or relatively time-consuming signal processing can beperformed and the reliability of the data Dωx, Dωy, Dωz, DAx, DAy, DAzis thus improved. However, the quantization error in A/D conversionincreases. Meanwhile, as the sampling period T becomes shorter, thequantization error decreases but the processing time to output data tothe host device 5 after acquiring the data Dωx, Dωy, Dωz, DAx, DAy, DAzbecomes shorter and therefore a large amount of signal processing orrelatively time-consuming signal processing cannot be performed. In thisway, the quantization error and the limitation to the signal processingare in a tradeoff relationship.

Therefore, the signal processing circuit 4 selects an optimum mode fromamong the first signal processing mode M1, the second signal processingmode M2, and the third signal processing mode M3 according to thesampling period T or the content of processing requested by the hostdevice 5 and thus takes balance between the quantization error and thelimitation to the signal processing. Each of the first signal processingmode M1, the second signal processing mode M2, and the third signalprocessing mode M3 will now be described.

First Signal Processing Mode M1

As shown in FIG. 3, in the first signal processing mode M1, the dataDωx, Dωy, Dωz, DAx, DAy, DAz outputted from the 3-axis angular velocitysensor device 2 and the 3-axis acceleration sensor device 3 areprocessed by the first signal processing unit 41, the second signalprocessing unit 42, and the third signal processing unit 43, and thedata Dωx3, Dωy3, Dωz3, DAx3, DAy3, DAz3 are outputted from the hostinterface 44 to the host device 5. That is, in the first signalprocessing mode M1, all the processing that can be performed by thesignal processing circuit 4 is performed on the data Dωx, Dωy, Dωz, DAx,DAy, DAz. Thus, more accurate data can be outputted to the host device5. Hereinafter, the processing time that is necessary to output the dataDωx3, Dωy3, Dωz3, DAx3, DAy3, DAz3 to the host device 5 after acquiringthe data Dωx, Dωy, Dωz, DAx, DAy, DAz is referred to as Tm1.

Second Signal Processing Mode M2

As shown in FIG. 4, in the second signal processing mode M2, the dataDωx, Dωy, Dωz, DAx, DAy, DAz outputted from the 3-axis angular velocitysensor device 2 and the 3-axis acceleration sensor device 3 areprocessed by the first signal processing unit 41 and the second signalprocessing unit 42, and the data Dωx2, Dωy2, Dωz2, DAx2, DAy2, DAz2 areoutputted from the host interface 44 to the host device 5. That is, thesecond signal processing mode M2 is a mode configured by omitting theprocessing by the third signal processing unit 43 from the first signalprocessing mode M1. As the processing by the third signal processingunit 43 is thus omitted, the processing time that is necessary to outputthe data Dωx2, Dωy2, Dωz2, DAx2, DAy2, DAz2 to the host device 5 afteracquiring the data Dωx, Dωy, Dωz, DAx, DAy, DAz can be made shorter thanthe processing time Tm1 in the first signal processing mode M1.Therefore, in the second signal processing mode M2, the sampling periodT can be set to be shorter than in the first signal processing mode M1.Hereinafter, the processing time that is necessary to output the dataDωx2, Dωy2, Dωz2, DAx2, DAy2, DAz2 to the host device 5 after acquiringthe data Dωx, Dωy, Dωz, DAx, DAy, DAz is referred to as Tm2 (<Tm1).

The data Dωx3, Dωy3, Dωz3, DAx3, DAy3, DAz3 outputted to the host device5 in the first signal processing mode M1 are, for example, attitude dataor position data acquired by computing and may not correspond to thedata Dωx, Dωy, Dωz, DAx, DAy, DAz outputted from the 3-axis angularvelocity sensor device 2 and the 3-axis acceleration sensor device 3.Meanwhile, the data Dωx2, Dωy2, Dωz2, DAx2, DAy2, DAz2 outputted to thehost device 5 in the second signal processing mode M2 may correspond tothe data Dωx, Dωy, Dωz, DAx, DAy, DAz outputted from the 3-axis angularvelocity sensor device 2 and the 3-axis acceleration sensor device 3. Inthis way, the signal processing circuit 4 may output data havingdifferent correspondence relationships with the individual sensorsaccording to the mode. In the second signal processing mode M2, the hostdevice 5 may compute attitude data or position data. The case where “theprocessing performed by the signal processing circuit 4 differs”includes the case where the content of the processing performed by thesignal processing unit 40 differs as shown in FIGS. 3 and 4 and alsoincludes the case where the data transmitted to outside from the hostinterface 44 differs.

Third Signal Processing Mode M3

The third signal processing mode M3 further includes an angular velocitymode M3ω where the data Dωx, Dωy, Dωz from the 3-axis angular velocitysensor device 2 are processed, and an acceleration mode M3A where thedata DAx, DAy, DAz from the 3-axis acceleration sensor device 3 areprocessed.

As shown in FIG. 5, in the angular velocity mode M3ω, the data Dωx, Dωy,Dωz outputted from the 3-axis angular velocity sensor device 2 areprocessed by the first signal processing unit 41 and the second signalprocessing unit 42, and the data Dωx2, Dωy2, Dωz2 are outputted from thehost interface 44 to the host device 5. That is, the angular velocitymode M3ω is a mode configured by omitting the processing of the dataDAx, DAy, DAz from the second signal processing mode. As the processingof the data DAx, DAy, DAz is thus omitted, the processing time that isnecessary to output the data Dωx2, Dωy2, Dωz2 to the host device 5 afteracquiring the data Dωx, Dωy, Dωz can be made shorter than the processingtime Tm2 in the second signal processing mode M2. Therefore, in theangular velocity mode M3ω, the sampling period T can be set to beshorter than in the second signal processing mode M2. Hereinafter, theprocessing time that is necessary to output the data Dωx2, Dωy2, Dωz2 tothe host device 5 after acquiring the data Dωx, Dωy, Dωz is referred toas Tm3 (<Tm2).

As shown in FIG. 6, in the acceleration mode M3A, the data DAx, DAy, DAzoutputted from the 3-axis acceleration sensor device 3 are processed bythe first signal processing unit 41 and the second signal processingunit 42, and the data DAx2, DAy2, DAz2 are outputted from the hostinterface 44 to the host device 5. That is, the acceleration mode M3A isa mode configured by omitting the processing of the data Dωx, Dωy, Dωzfrom the second signal processing mode. As the processing of the dataDωx, Dωy, Dωz is thus omitted, the processing time that is necessary tooutput the data DAx2, DAy2, DAz2 to the host device 5 after acquiringthe data DAx, DAy, DAz can be made shorter than the processing time Tm2in the second signal processing mode M2. Therefore, in the accelerationmode M3A, the sampling period T can be set to be shorter than in thesecond signal processing mode M2. Hereinafter, the processing time thatis necessary to output the data DAx2, DAy2, DAz2 to the host device 5after acquiring the data DAx, DAy, DAz is referred to as Tm3 (<Tm2). Thetime taken for signal processing is substantially the same in theangular velocity mode M3ω and in the acceleration mode M3A. Therefore,in this embodiment, the same processing time Tm3 is employed. However,this is not limiting. The processing time may differ between thesemodes.

The first signal processing mode M1, the second signal processing modeM2, and the third signal processing mode M3 have been described above.The mode selection circuit 45 switches the processing mode according tothe signal processing requested by the host device 5, for example.

The signal processing circuit 4 performs signal processing in the firstsignal processing mode M1 when the data Dωx3, Dωy3, Dωz3, DAx3, DAy3,DAz3 are requested by the host device 5. A sampling period T1 in thiscase can be suitably set, using the processing time Tm1 as the lowerlimit value. The sampling period T1 may be preferably set to be equal tothe processing time Tm1. Thus, the sampling period T can be made asshort as possible and the quantization error can be reduced. Therefore,balance can be taken between the quantization error and the limitationto the signal processing while the content of signal processing isprioritized. For example, the data Dωx3, Dωy3, Dωz3, DAx3, DAy3, DAz3are a “first data set” in the claims.

The signal processing circuit 4 performs signal processing in the secondsignal processing mode M2 when the data Dωx2, Dωy2, Dωz2, DAx2, DAy2,DAz2 are requested by the host device 5. A sampling period T2 in thiscase can be suitably set, using the processing time Tm2 as the lowerlimit value and the processing time Tm1 as the upper limit value. Thesampling period T2 may be preferably set to be equal to the processingtime Tm2. Thus, the sampling period T can be made as short as possibleand the quantization error can be reduced. Therefore, balance can betaken between the quantization error and the limitation to the signalprocessing while the content of signal processing is prioritized. Forexample, the data Dωx2, Dωy2, Dωz2, DAx2, DAy2, DAz2 are a “second dataset” in the claims. The sampling period T2 in the second signalprocessing mode M2 is shorter than the sampling period T1 in the firstsignal processing mode M1.

The signal processing circuit 4 performs signal processing in theangular velocity mode M3ω of the third signal processing mode M3 whenthe data Dωx2, Dωy2, Dωz2 are requested by the host device 5. A samplingperiod T3ω in this case can be suitably set, using the processing timeTm3 as the lower limit value and the processing time Tm2 as the upperlimit value. The sampling period T3ω may be preferably set to be equalto the processing time Tm3. Thus, the sampling period T can be made asshort as possible and the quantization error can be reduced. Therefore,balance can be taken between the quantization error and the limitationto the signal processing while the content of signal processing isprioritized. The sampling period T3ω in the angular velocity mode M3ω ofthe third signal processing mode M3 is shorter than the sampling periodT1 in the first signal processing mode M1 and the sampling period T2 inthe second signal processing mode M2. For example, the data Dωx2, Dωy2,Dωz2 may be referred to as a “third data set”.

The signal processing circuit 4 performs signal processing in theacceleration mode M3A of the third signal processing mode M3 when thedata DAx2, DAy2, DAz2 are requested by the host device 5. A samplingperiod T3A in this case can be suitably set, using the processing timeTm3 as the lower limit value. The sampling period T3A may be preferablyset to be equal to the processing time Tm3. Thus, the sampling period Tcan be made as short as possible and the quantization error can bereduced. Therefore, balance can be taken between the quantization errorand the limitation to the signal processing while the content of signalprocessing is prioritized. The sampling period T3A in the accelerationmode M3A of the third signal processing mode M3 is shorter than thesampling period T1 in the first signal processing mode M1 and thesampling period T2 in the second signal processing mode M2. For example,the data DAx2, DAy2, DAz2 may be referred to as a “fourth data set”.

Such a configuration enables output of requested data to the host device5 in a shorter sampling period T. Therefore, balance can be takenbetween the quantization error and the limitation to the signalprocessing while the content of signal processing is prioritized.

The case where the signal processing mode is switched according to thesignal processing requested by the host device 5 has been describedabove. Other than this method, the signal processing circuit 4 mayswitch the signal processing mode according to the sampling period Trequested by the host device 5.

The signal processing circuit 4 performs signal processing in the firstsignal processing mode M1 when the sampling period T requested by thehost device 5 is equal to or longer than the processing time Tm1. Thus,all the signal processing that can be performed by the signal processingcircuit 4 is performed and more accurate data can be outputted to thehost device 5. Therefore, balance can be taken between the quantizationerror and the limitation to the signal processing while the samplingperiod T is prioritized.

The signal processing circuit 4 performs signal processing in the secondsignal processing mode M2 when the sampling period T requested by thehost device 5 is equal to or longer than the processing time Tm2 andshorter than the processing time Tm1. Thus, as much processing aspossible can be performed within the requested sampling period T anddata with as high accuracy as possible can be outputted to the hostdevice 5. Therefore, balance can be taken between the quantization errorand the limitation to the signal processing while the sampling period Tis prioritized.

The signal processing circuit 4 performs signal processing in the thirdsignal processing mode M3 when the sampling period T requested by thehost device 5 is equal to or longer than the processing time Tm3 andshorter than the processing time Tm2. Thus, as much processing aspossible can be performed within the requested sampling period T anddata with as high accuracy as possible can be outputted to the hostdevice 5. Therefore, balance can be taken between the quantization errorand the limitation to the signal processing while the sampling period Tis prioritized. Whether to select the angular velocity mode M3ω or theacceleration mode M3A can be suitably decided. Also, for example,alternately switching between the angular velocity mode M3ω and theacceleration mode M3A enables the data Dωx, Dωy, Dωz about angularvelocity and the data DAx, DAy, DAz about acceleration to be alternatelyoutputted to the host device 5. Therefore, the host device 5 can acquirethe data about all the six axes.

Such a configuration enables the execution of as much processing aspossible within the requested sampling period T and the output of datawith as high accuracy as possible to the host device 5. Therefore,balance can be taken between the quantization error and the limitationto the signal processing while the sampling period T is prioritized.

The measurement system 10 has been described above. The sensor module 1included in such a measurement system 10 has the 3-axis angular velocitysensor device 2 and the 3-axis acceleration sensor device 3, which areinertial sensors, and the signal processing circuit 4, which is aprocessing circuit processing the data Dωx, Dωy, Dωz, DAx, DAy, DAz,which are output signals from the 3-axis angular velocity sensor device2 and the 3-axis acceleration sensor device 3, as described above. Thesignal processing circuit 4 varies the processing of the data Dωx, Dωy,Dωz, DAx, DAy, DAz according to the sampling period T for acquiring thedata Dωx, Dωy, Dωz, DAx, DAy, DAz. Such a configuration enables theexecution of as much signal processing as possible within the requestedsampling period T. Therefore, balance can be taken between thequantization error and the limitation to the signal processing while thesampling period T is prioritized.

As described above, the signal processing circuit 4 makes the number ofprocessing steps for the data Dωx, Dωy, Dωz, DAx, DAy, DAz smaller asthe sampling period T becomes shorter. That is, the signal processingcircuit 4 performs signal processing in the first signal processing modeM1 when the sampling period T is equal to or longer than the processingtime Tm1, and performs signal processing in the second signal processingmode M2 having fewer processing steps than the first signal processingmode M1, when the sampling period T is equal to or longer than theprocessing time Tm2 and shorter than the processing time Tm1. Thus, thetime taken for signal processing can more easily fall within therequested sampling period T and balance can be taken between thequantization error and the limitation to the signal processing.

As described above, the signal processing circuit 4 has the first signalprocessing unit 41, the second signal processing unit 42, and the thirdsignal processing unit 43 as a plurality of signal processing unitsperforming different types of processing on the data Dωx, Dωy, Dωz, DAx,DAy, DAz, and processes the data Dωx, Dωy, Dωz, DAx, DAy, DAz by moresignal processing units as the sampling period T becomes longer. Thatis, the signal processing circuit 4 performs signal processing by thefirst signal processing unit 41, the second signal processing unit 42,and the third signal processing unit 43 when the sampling period T isequal to or longer than the processing time Tm1, and performs signalprocessing by the first signal processing unit 41 and the second signalprocessing unit 42 when the sampling period T is equal to or longer thanthe processing time Tm2 and shorter than the processing time Tm1. Thus,the time taken for signal processing can more easily fall within therequested sampling period T and balance can be taken between thequantization error and the limitation to the signal processing.

As described above, the sensor module 1 has the 3-axis angular velocitysensor device 2 and the 3-axis acceleration sensor device 3 as aplurality of inertial sensors, and the signal processing circuit 4processes output signals from more inertial sensors as the samplingperiod T becomes longer. That is, the signal processing circuit 4performs signal processing on output signals from both the 3-axisangular velocity sensor device 2 and the 3-axis acceleration sensordevice 3 when the sampling period T is equal to or longer than theprocessing time Tm2, and performs signal processing only on an outputsignal from one of the 3-axis angular velocity sensor device 2 and the3-axis acceleration sensor device 3 when the sampling period T isshorter than the processing time Tm2. Thus, the time taken for signalprocessing can more easily fall within the requested sampling period Tand balance can be taken between the quantization error and thelimitation to the signal processing.

As described above, the sensor module 1 has the 3-axis angular velocitysensor device 2 and the 3-axis acceleration sensor device 3, which areinertial sensors, and the signal processing circuit 4, which is aprocessing circuit processing the data Dωx, Dωy, Dωz, DAx, DAy, DAz,which are output signals from the 3-axis angular velocity sensor device2 and the 3-axis acceleration sensor device 3. The signal processingcircuit 4 changes the sampling period T for acquiring the data Dωx, Dωy,Dωz, DAx, DAy, DAz according to the content of processing of the dataDωx, Dωy, Dωz, DAx, DAy, DAz. Such a configuration enables the output ofrequested data in a shorter sampling period T. Therefore, balance can betaken between the quantization error and the limitation to the signalprocessing while the content of signal processing is prioritized.

As described above, the signal processing circuit 4 makes the samplingperiod T shorter as the number of processing steps for the data Dωx,Dωy, Dωz, DAx, DAy, DAz becomes smaller. That is, the sampling period Tin the second signal processing mode M2, where signal processing isperformed by the first signal processing unit 41 and the second signalprocessing unit 42, is made shorter than the sampling period T in thefirst signal processing mode M1, where signal processing is performed bythe first signal processing unit 41, the second signal processing unit42, and the third signal processing unit 43. Thus, balance can be takenmore effectively between the quantization error and the limitation tothe signal processing.

As described above, the signal processing circuit 4 has the first signalprocessing unit 41, the second signal processing unit 42, and the thirdsignal processing unit 43 as a plurality of signal processing unitsperforming different types of processing on the data Dωx, Dωy, Dωz, DAx,DAy, DAz, and makes the sampling period T longer as the number of signalprocessing units processing the data Dωx, Dωy, Dωz, DAx, DAy, DAzbecomes greater. That is, the sampling period T in the second signalprocessing mode M2, where signal processing is performed by the firstsignal processing unit 41 and the second signal processing unit 42, ismade shorter than the sampling period T in the first signal processingmode M1, where signal processing is performed by the first signalprocessing unit 41, the second signal processing unit 42, and the thirdsignal processing unit 43. Thus, balance can be taken more effectivelybetween the quantization error and the limitation to the signalprocessing.

As described above, the 3-axis angular velocity sensor device 2 and the3-axis acceleration sensor device 3 as a plurality of inertial sensorsare provided, and the signal processing circuit 4 makes the samplingperiod T longer as the number of inertial sensors processing an outputsignal becomes greater. That is, the sampling period T in the first andsecond signal processing modes M1, M2, where signal processing isperformed on output signals from both the 3-axis angular velocity sensordevice 2 and the 3-axis acceleration sensor device 3, is made longerthan the sampling period T in the third signal processing mode M3, wheresignal processing is performed only on an output signal from one of the3-axis angular velocity sensor device and the 3-axis acceleration sensordevice 3. Thus, balance can be taken between the quantization error andthe limitation to the signal processing.

As described above, the sensor module 1 has the 3-axis angular velocitysensor device 2 and the 3-axis acceleration sensor device 3, which areinertial sensors, and the signal processing circuit 4, which is aprocessing circuit processing the data Dωx, Dωy, Dωz, DAx, DAy, DAz,which are output signals from the 3-axis angular velocity sensor device2 and the 3-axis acceleration sensor device 3. The signal processingcircuit 4 sets the content of processing to be performed on the dataDωx, Dωy, Dωz, DAx, DAy, DAz from the 3-axis angular velocity sensordevice 2 and the 3-axis acceleration sensor device 3 and the samplingperiod T for acquiring the data Dωx, Dωy, Dωz, DAx, DAy, DAz from the3-axis angular velocity sensor device 2 and the 3-axis accelerationsensor device 3, according to data requested by the host device 5. Thus,the sampling period T can be made as short as possible and thequantization error can be reduced. Therefore, balance can be takenbetween the quantization error and the limitation to the signalprocessing while the content of signal processing is prioritized.

As described above, a first mode where the sampling period T is set tobe a first period when the data requested by the host device 5 is afirst data set, and a second mode where the sampling period T is set tobe a second period that is shorter than the first period when the datarequested by the host device 5 is a second data set that is differentfrom the first data set, are provided. The signal processing circuit 4executes the switching between a plurality of modes including the firstmode and the second mode. In this embodiment, one of the first signalprocessing mode M1, the second signal processing mode M2, and the thirdsignal processing mode M3 is the first mode and any of the other two isthe second mode. Such a configuration enables the output of requesteddata to the host device 5 in a shorter sampling period T. Therefore,balance can be taken between the quantization error and the limitationto the signal processing while the content of signal processing isprioritized.

As described above, the measurement system 10 has the sensor module 1and the host device 5 electrically coupled to the sensor module 1. Thus,the measurement system 10 can achieve the effects of the sensor module1.

Second Embodiment

FIG. 7 is a block diagram showing an overall configuration of ameasurement system according to a second embodiment. FIG. 8 is a blockdiagram showing signal processing in a third signal processing mode.

The measurement system 10 according to this embodiment is similar to themeasurement system 10 according to the first embodiment, except forhaving two sensor modules 1. In the description below, this embodimentis described mainly in terms of the difference from the foregoingembodiment and the description of similar matters is omitted. In FIGS. 7and 8, components similar to those in the foregoing embodiment aredenoted by the same reference signs.

As shown in FIG. 7, in this embodiment, two sensor modules LA, 1B arecoupled together in a synchronized state. In the illustratedconfiguration, the sensor modules 1A, 1B are synchronized with eachother, based on an oscillation signal outputted from an oscillator 46installed in the signal processing circuit 4 of the sensor module LA.The sensor modules 1A, 1B and the host device 5 are coupled together viaan SPI (serial peripheral interface), for example. However, the methodfor coupling these components is not particularly limited.

In the first signal processing mode M1 and the second signal processingmode M2, signal processing is performed using one or both of the sensormodules 1A, 1B. The processing method is similar to the processingmethod in the first embodiment and therefore the description thereof isomitted. Meanwhile, in the third signal processing mode M3, signalprocessing is performed using one of the sensor modules 1A, 1B. Thethird signal processing mode M3 will now be described in detail.

In the first embodiment, only one sensor module 1 is used. Therefore, inthe third signal processing mode M3, data about all the six axes cannotbe outputted to the host device 5 unless the angular velocity mode M3ωand the acceleration mode M3A are switched alternately.

Meanwhile, in this embodiment, two sensor modules 1A, 1B are used.Therefore, the sensor module 1A is set in the angular velocity mode M3ωand the sensor module 1B is set in the acceleration mode M3A, as shownin FIG. 8. Thus, data about all the six axes can be simultaneouslyoutputted to the host device 5. Therefore, the output rate can beincreased to twice the output rate in the first embodiment.

Such a second embodiment can achieve effects similar to those of thefirst embodiment described above.

The sensor module and the measurement system according to the presentdisclosure have been described above, based on the illustratedembodiments. However, the present disclosure is not limited to theseembodiments. The configuration of each part can be replaced with anyconfiguration having a similar function. Also, any other component maybe added to the present disclosure. The embodiments described above maybe combined together according to need.

For example, while the signal processing unit 40 in the embodimentsdescribed above has the first signal processing unit 41, the secondsignal processing unit 42, and the third signal processing unit 43, thisis not limiting. One of these units may be omitted. Also, the signalprocessing unit 40 may have at least one other signal processing unit.The content of signal processing in each signal processing mode is notparticularly limited. While the first signal processing mode M1, thesecond signal processing mode M2, and the third signal processing modeM3 are provided in the embodiments described above, this is notlimiting. One of these modes may be omitted. Also, further at least oneother signal processing mode may be provided.

What is claimed is:
 1. A sensor module comprising: an inertial sensor;and a processing circuit processing an output signal from the inertialsensor, the processing circuit varying processing of the output signalaccording to a sampling period for acquiring the output signal.
 2. Thesensor module according to claim 1, wherein the processing circuit makesa number of processing steps for the output signal smaller as thesampling period becomes shorter.
 3. The sensor module according to claim1, wherein the processing circuit has a plurality of signal processingunits performing different types of processing from each other on theoutput signal, and processes the output signal by more of the signalprocessing units as the sampling period becomes longer.
 4. The sensormodule according to claim 1, further comprising: a plurality of theinertial sensors, wherein the processing circuit processes the outputsignal from more of the inertial sensors as the sampling period becomeslonger.
 5. A sensor module comprising: an inertial sensor; and aprocessing circuit processing an output signal from the inertial sensor,the processing circuit changing a sampling period for acquiring theoutput signal according to a content of processing of the output signal.6. The sensor module according to claim 5, wherein the processingcircuit makes the sampling period shorter as a number of processingsteps for the output signal becomes smaller.
 7. The sensor moduleaccording to claim 6, wherein the processing circuit has a plurality ofsignal processing units performing different types of processing fromeach other on the output signal, and makes the sampling period longer asa number of the signal processing units processing the output signalbecomes greater.
 8. The sensor module according to claim 5, furthercomprising: a plurality of the inertial sensors, wherein the processingcircuit makes the sampling period longer as a number of the inertialsensors processing the output signal becomes greater.
 9. A sensor modulecomprising: an inertial sensor; and a processing circuit processing anoutput signal from the inertial sensor, the processing circuit setting acontent of processing to be performed on the output signal from theinertial sensor and a sampling period for acquiring the output signalfrom the inertial sensor, according to data requested by a host device.10. The sensor module according to claim 9, comprising: a first modewhere the sampling period is set to be a first period when the datarequested by the host device is a first data set, and a second modewhere the sampling period is set to be a second period that is shorterthan the first period when the data requested by the host device is asecond data set that is different from the first data set, wherein theprocessing circuit executes switching between a plurality of modesincluding the first mode and the second mode.
 11. A measurement systemcomprising: the sensor module according to claim 1; and a host deviceelectrically coupled to the sensor module.